MB Pro 15 inch 2018 memory configuration

Dr. McKay

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As the 2018 Macbook Pro's memory is not upgradeable, I'm wondering whether to go for 16Gb or 32Gb of RAM.
16Gb would be plenty for what I want to do with it but I'm under the impression that MB Pro's with 16Gb come with just one memory slot filled.
Does this mean you only get dual-channel memory when you go for 32Gb of RAM or is there no speed difference at all between a MB Pro with 16 or 32Gb of RAM ?

I could get a very good deal on a new 15 inch 2.6Ghz model with a 512Gb SSD, but with 16Gb of RAM. The promotion is only on the 16Gb model so if I want 32Gb of RAM I'm going to have to pay full price...
 

treekram

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Nov 9, 2015
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On my 2018 15" 2.2Ghz MBP, the System Information app shows 2 banks of RAM, specifically saying "ChannelA" and "ChannelB" are being used so when you get the 32GB version, I'm guessing you get RAM chips that are double the density. I always have gotten two banks of memory in my computers where memory is upgradable but for one of them, I waited a few months before getting the second bank. I couldn't tell the difference between using one module or two so even if there was only one bank, I'd get that model if it had a price promotion and the double-bank model didn't.

Update: Looking at the System Information more closely, it does same "Bank 0/Channel A-DIMM0" so perhaps the 32GB model has a DIMM0 and DIMM1 not chips with 2x the density. I haven't seen detailed teardowns of the 16GB and 32GB models. The iFixit video shows 4 RAM chips on one side of the logic board for the 16GB model.
 

Dr. McKay

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Thanks for the reply, but could someone else confirm this ? Does the 16Gb model come with 1x16Gb or 2x8Gb ?
And more importantly, is there a speed difference between dual channel and single channel. I'm not a techie so for all I know, there is no speed difference at all because of the motherboard infrastructure...

I could buy the new MB Pro 2.6Ghz with a 512 Gb SSD and 16Gb of RAM for the price of the base 2.2Ghz and 256Gb SSD, from a authorized reseller, so definitely no scam. They just do weekly promotions of certain models so I have to act quickly... (I live in Belgium, in case you're wondering ;) )
 

jerryk

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Nov 3, 2011
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I don't think you will see much speed difference by increasing. And the Macbook memory is pretty fast.

Is there a specific application you run that is dependent on high speed memory for reasonable performance?
[doublepost=1551128916][/doublepost]
Thanks for the reply, but could someone else confirm this ? Does the 16Gb model come with 1x16Gb or 2x8Gb ?
And more importantly, is there a speed difference between dual channel and single channel. I'm not a techie so for all I know, there is no speed difference at all because of the motherboard infrastructure...

I could buy the new MB Pro 2.6Ghz with a 512 Gb SSD and 16Gb of RAM for the price of the base 2.2Ghz and 256Gb SSD, from a authorized reseller, so definitely no scam. They just do weekly promotions of certain models so I have to act quickly... (I live in Belgium, in case you're wondering ;) )
As treekram said there are 4 chips on the 16 GB main board. With the 2012 and beyond MacBooks all memory is soldered on the main board in memory modules, and is not upgradable without replacing the system. These memory modules are quite different than the RAM sticks of memory you might be used to from desktop PC and other companies laptops that come in 1 X 16GB or 2 X 8GB formats from vendors like G.Skill, Corsair etc.
 
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Dr. McKay

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I don't think you will see much speed difference by increasing. And the Macbook memory is pretty fast.

Is there a specific application you run that is dependent on high speed memory for reasonable performance?
[doublepost=1551128916][/doublepost]

As treekram said there are 4 chips on the 16 GB main board. With the 2012 and beyond MacBooks all memory is soldered on the main board in memory modules, and is not upgradable without replacing the system. These memory modules are quite different than the RAM sticks of memory you might be used to from desktop PC and other companies laptops that come in 1 X 16GB or 2 X 8GB formats from vendors like G.Skill, Corsair etc.
So nothing to with the memory configuration of an iMac, for example ?
 

treekram

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Nov 9, 2015
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Thanks for the reply, but could someone else confirm this ? Does the 16Gb model come with 1x16Gb or 2x8Gb ?
And more importantly, is there a speed difference between dual channel and single channel. I'm not a techie so for all I know, there is no speed difference at all because of the motherboard infrastructure...

I could buy the new MB Pro 2.6Ghz with a 512 Gb SSD and 16Gb of RAM for the price of the base 2.2Ghz and 256Gb SSD, from a authorized reseller, so definitely no scam. They just do weekly promotions of certain models so I have to act quickly... (I live in Belgium, in case you're wondering ;) )
There is a speed difference in using 2 banks vs. 1 bank of RAM presuming the computer is designed to take advantage of dual-bank memory - one article says 16-17% but even at that the author of the paper says you "would not be sacrificing anything significant" (by using single-channel RAM). But this doesn't matter since the MBP uses dual-channel RAM - it's certainly your right to get a second confirmation but to me, you'd be spending quite a bit more money simply because you couldn't get a second (or third confirmation). You also misunderstand - RAM chips have Gb not GB designations. So if the 16GB MBP had 4 chips (and it's hard to tell because it might be stacked and the pictures I've seen are not detailed enough to see), it would mean they had 32Gb chips. As jerryk mentioned, these MBP's don't use memory sticks - they use individual RAM chips soldered to the logic board so you can't refer to the size as 1x16GB or 2x8GB - it's more like 4x32Gb or 8x16Gb.
https://beebom.com/single-channel-vs-dual-channel-memory/
 

jerryk

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Nov 3, 2011
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So nothing to with the memory configuration of an iMac, for example ?
If you mean in terms of memory modules like those found in an iMac, no they are different. Those are replaceable modules in a industry standard package that are inserted into slots and can be swapped with different parts from multiple vendors.

The macBook Pros Retina units (circa 2013 or later) chips are soldered to the main board for RAM. They are no user replaceable or up-gradable, except by pulling a credit card to buy a new machine.

Also, starting with the 2016 Macbook Pros, with touchbar, onward the SSD is a set of chips soldered to the main board so the SSD is also not user replacable or upgradable except with a credit card.

To see the details watch this video, specifically at 0:30

 

Dr. McKay

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On another note, I have found a 15 inch mid 2015 MB Pro with 512Gb SSD, 16Gb of RAM and discreet graphics. This model :
https://everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-i7-2.5-15-dual-graphics-mid-2015-retina-display-specs.html

It's far from being as fast as the new models but it would be sufficient for my needs (I also have a 2017 27 inch iMac to do the 'heavy lifting').
The used MB Pro is in mint condition, I'm just waiting on confirmation on the battery status (charge cycles, etc.). Asking price is 1500 euro (around 1700 dollar) but it's negotiable (a new 15 inch MB Pro 2.6Ghz, 16Gb of RAM and 512Gb SSD would set me back 2800 euro, that's around 3200 dollar (that's with the current promotion which ends on Friday, it normally costs around 500 euro more).

I believe I would be good for quite a few years as far as OS updates go. Plus, I understand these mid-2015 MB Pro's are kind of sought after...
Are they reliable, these mid 2015 models or are there things I should be aware of ?
 
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Natzoo

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Sep 16, 2014
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On another note, I have found a 15 inch mid 2015 MB Pro with 512Gb SSD, 16Gb of RAM and discreet graphics. This model :
https://everymac.com/systems/apple/macbook_pro/specs/macbook-pro-core-i7-2.5-15-dual-graphics-mid-2015-retina-display-specs.html

It's far from being as fast as the new models but it would be sufficient for my needs (I also have a 2017 27 inch iMac to do the 'heavy lifting').
The used MB Pro is in mint condition, I'm just waiting on confirmation on the battery status (charge cycles, etc.). Asking price is 1500 euro (around 1700 dollar) but it's negotiable (a new 15 inch MB Pro 2.6Ghz, 16Gb of RAM and 512Gb SSD would set me back 2800 euro, that's around 3200 dollar (that's with the current promotion which ends on Friday, it normally costs around 500 euro more).

I believe I would be good for quite a few years as far as OS updates go. Plus, I understand these mid-2015 MB Pro's are kind of sought after...
Are they reliable, these mid 2015 models or are there things I should be aware of ?
I had the same machine before upgrading to the 2018 version, honestly the 2015 still works great and will be useful for at least the next couple of years. And honestly, rumors are saying that the refreshed version is coming this or next year, so I would wait.
 

Dr. McKay

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I had the same machine before upgrading to the 2018 version, honestly the 2015 still works great and will be useful for at least the next couple of years. And honestly, rumors are saying that the refreshed version is coming this or next year, so I would wait.
I know there 's a new MB Pro coming with a redesign, and the prospect of a 16 inch laptop appeals to me. Only, the price that Apple will be charging for it will undoubtedly be very very high, seeing their track record.
I'm negotiating the price so I could have the mid 2015 model for 1300 to 1400 euro, a 15 inch 2018 model would set me back 3000 euro...
Battery capacity is still at 87% so not bad for a 3 year old machine (it's a mid 2015 model but he bought it new in early 2016).
 

Dr. McKay

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Found another one, also a mid 2015 MB Pro 15 inch, but this is the base 2.2Ghz model, 16Gb of RAM, but with a 256Gb SSD and just the Iris Pro graphics (as opposed to the other one with 512Gb SSD and Radeon dedicated graphics).
It's cheaper, though, at only 1000 euro and in mint condition with only 197 battery cycles...

I would be doing some light photo editing and some occasional 1080p video editing on it (certainly not 4K). The 512Gb SSD in the 2.5Ghz model is nice but 256gb would be sufficient as I also have a 27 inch iMac with ample storage. But would I feel the lack of the dedicated Radeon 390M with 2Gb of VRAM for my use case ?
 

alex87f

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Jun 24, 2015
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Ultimately went for the 2.5Ghz model with Radeon graphics. Knocked the price down to 1200 euro.
Seems like a fair price - I also live in Belgium and recently look at the used mac market (2ememain/2dehands.be, I guess :) ), and based on what I've seen this sounds like a decent deal.

(and I also just bought a used retina Macbook, although a 13" in my case)
 
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